Borisov told voters that he was stepping down after the marches turned violent, which he said he could not take.

"I cannot stand looking at a bloody Eagles' Bridge," he said, referring to a downtown intersection in the capital of Sofia where police and protesters violently clashed. "Every drop of blood is a shame for us."

Those demonstrations pitted flare-wielding demonstrators against truncheon-carrying officers. Fourteen people were injured in the violence.

The demonstrations Wednesday were just the latest chaos in the Eastern European nation, the EU's poorest member, where average salaries are just 380 euros a month. On Sunday, 100,000 protesters took to the streets, pasting government buildings in downtown Sofia with eggs and tomatoes and lashing out at police.

The protesters burned power bills and they denounced Borisov's government for failing to improve living standards in the country.

Electricity bills have gone up 13% since July. For many protesters the rising cost brings back memories of Bulgaria's communist past and the poverty prevalent during that period. Borisov announced Tuesday that the Czech utility CEZ, which controls power distribution in western Bulgaria, would be stripped of its license. CEZ says rates were set by the Bulgarian government according to a contract with the utility.

"People feel they have been lied to time and again during the entire transition period (since 1989), said Petar Georgiev, who was protesting. "They are sick of the politicians."

Bulgaria, a former communist country of 7 million people, held its first free multiparty elections since World War II in 1990. Borisov began his post-communist career in the 1990s as a top bodyguard to the elites of Bulgarian politics, guarding former kings and communists. His center-right government won office in 2009 on promises to raise living standards and end corruption.

The government started off popular, but it lost voters as economic conditions worsened because of recession. On Tuesday he fired his deputy and finance minister Simeon Djankov after protests in Sofia. And Borisov promised to punish price-gouging foreign power companies.

"Firing Djankov was clearly a desperate move by Borisov to salvage his own reputation," said independent analyst Veselin Avraamov, who predicted the protests. "After that failed, the resignation can be seen as a similar move: (It aims to) avoid becoming the sole target of popular anger."

Protesters accused Bulgaria's political class of having ties to organized crime.

"Bulgaria has, unfortunately, become notorious for its contract killings, said Johanna Deimel, the deputy director of Southeast Europe Association, a research institute in Germany. "A lot of contract killings of prominent figures have never been solved."

With its prime minister gone, Bulgaria's elections, scheduled for July, will now be moved forward to April or May. Already, some analysts are predicting a "dirty" campaign. Protesters say that they won't be won over by the opposition â?? much less the government.

"Opposition parties are already trying to ride the wave (of anger) and use the demonstrations for their own gain," Georgiev said. "The electricity bills were just the spark."